Synthesis, Crystal Structures and Magnetic Properties of Lanthanide Complexes with Rhodamine Benzoyl Hydrazone Ligands

Given the outstanding magnetic characteristics of lanthanide ions, the development of lanthanide complexes, transitioning from mononuclear to multinuclear, becomes imperative. Previous research utilized rhodamine Schiff base ligands to synthesize a series of mononuclear complexes exhibiting remarkable single-molecule magnetic properties alongside fluorescence characteristics. In the current study, we designed analogous ligands to synthesize complexes [Dy(HL1-o)(NO3)2(CH3OH)2]NO3·CH3OH (complex 1) and tetranuclear [Ln4(L1-c)2(L2)2(μ3-OH)2(NO3)2(CH3OH)4](NO3)2·2CH3CN·5CH3OH·2H2O (Ln = Dy, complex 2; Ln = Gd, complex 3), spanning from mononuclear to tetranuclear molecules. Magnetic susceptibility measurements show that 1 is a single-molecule magnet with Ueff = 33.2(10) K, 2 shows slow magnetic relaxation and 3 is a magnetic cooling material with the magnetic entropy change of 9.81 J kg−1 K−1 at 2 K and 5 T.